Tests were performed using green fir sawdust @44% moisture in a prototype cookstove model named "Helen" designed by Larry Dobson.

Due to very low draft caused by extremely hot summer test conditions, the maximum burn-rate of 50,000 Btu/hr (14.7Kw) was not achieved during these tests Likewise, the low-burn of estimated 8,000Btu/hr was forced to be prematurely terminated when flue gases became cooler than the outside temperature (95°F), creating a negative draft.